As the electronic and electric appliances are reduced in size recently, component parts are also reduced in size and advanced in definition, and high definition and high precision are demanded in machining of parts at machining precision of +/−50 μm or less. In the conventional press processing or blanking process, the precision is about +/−100 μm at most, and such demand cannot be satisfied. Drilling of materials is also demanded to conform to high definition and high precision, and drilling by using conventional drill or die cannot meet the needs.
To solve the problems, lately, machining of materials by using laser beam is attracting wide attention. In particular, the machining method by ultraviolet absorption ablation of laser beam of small heat damage and high definition is noticed as precise outline processing method or fine drilling method.
As the background art, for example, the dicing method of workpiece includes a method of dicing the workpiece by laser beam while supporting and fixing the workpiece on a dicing sheet (Japanese Laid-open Patent No. 2002-343747). Also proposed is a method of dicing a semiconductor wafer by combining laser with water micro jet (Japanese Laid-open Patent No. 2003-34780). The dicing sheet mentioned in these patent publications is disposed at the exit side of laser beam of the workpiece, and is used for supporting and fixing the workpiece (to be processed by laser) during dicing and in the subsequent processes.
When laser beam is used, it requires aftertreatment called desmearing in order to remove deposits of decomposition products of carbon or the like generated by laser processing from the surface of workpiece. The sticking strength of decomposition products is firm in proportion to power of laser beam, and when the power of laser beam is increased, it is difficult to remove deposits in aftertreatment. A stubborn decomposition product may be generally removed by wet desmearing using an aqueous solution of potassium permanganate or the like, but the wet desmearing is accompanied by heavy environmental burden of such as waste liquid treatment. In particular, at the side contacting with the processing table of workpiece or adhesive sheet (the laser beam exist side) is likely to be coated not only with the decomposition products of workpiece but also with decomposition products of processing table and adhesive sheet. As a result, improvement of throughput of processing is impeded, or reliability of cutting or drilling is lowered.